1. Field of the Invention
This invention relates to the enhanced detection of non-voice information on a telephone line by an adjunct call related information (e.g., Caller ID) unit associated with customer premises equipment. More particularly, it relates to the ability to eliminate or suppress voice signals at an adjunct call related information receiver unit while the associated customer premises equipment is in an off-hook condition, allowing improved detection of the call related information.
2. Background of Related Art
Call information is useful to users of a telephone system. For example, a well known and popular call information service provided in the United States is Calling Identity Delivery (Caller ID). This service typically provides the telephone number and household name information of a calling party to the called party before the call is answered. Based on a display of the call information, the called party may decide not to answer the incoming call. Basic call information such as Caller ID information is transmitted from the local telephone company to the called party while the called party""s telephone is in a hung-up or on-hook state, e.g., between the first and second rings.
Another telephone company service which has become well known and popular is that which allows a third party to call while the telephone is off-hook, currently implemented in the United States in Call Waiting services provided by telephone companies. Call waiting allows someone who is already using the telephone (i.e., in an off-hook state), to receive an audible interruption, click or other indication at the customer premises equipment that another person is calling, and then to establish a connection with the third party caller without hanging up on the first party.
More recently, call information has been combined with third party caller services to provide an advanced service currently known as Calling Identity Delivery on Call Waiting (CIDCW) in the United States. CIDCW service allows a customer, while off-hook on an existing call, to receive information about an incoming calling party on a waited call before answering that incoming call waiting call. A customer premises equipment (CPE) Alerting Signal (CAS) is transmitted to the CPE to indicate the availability of call related information. The CAS is a short burst of a combination of high frequencies that are appended to the Subscriber Alerting Signal (SAS) otherwise known as the xe2x80x98Call Waiting Tonexe2x80x99. Using CIDCW, a user can decide whether or not to take the incoming call waiting call.
Customer premises equipment capable of receiving on-hook call information such as Caller ID (CID) including Calling Number Delivery (CND) and Calling Name Delivery (CNAM), is generally referred to as Type I customer premises equipment. Customer premises equipment additionally capable of receiving call information when off-hook or already in an established call with another party (CIDCW) is generally referred to as a Type II customer premises equipment. With Type II customer premises equipment and Caller ID service, the called party is alerted to the availability of call information for an incoming call waiting call with an alerting CAS tone. The alerting CAS tone is acknowledged with a DTMFD, and the FSK data corresponding to the call information follows from the central office to the customer premises equipment.
In the United States, FSK call information such as Caller ID generally is not transmitted in conventional schemes by the central office unless an acknowledge (ACK) signal is received from the customer premises equipment. Of course, the call information may be transmitted without implementation of an acknowledge signal. The central office typically silences the far-end party""s voice path before the alerting CAS sequence is provided. Likewise, Type II call related information receivers which are integrated with customer premises equipment (hereinafter xe2x80x9cintegrated CIDCW unitsxe2x80x9d) mute the handset (or microphone and speaker of a speakerphone) before sending the ACK signal. The central office sends FSK caller ID call information using the signaling protocol described in Bellcore recommendation TR-NWT-000030. Upon completion of the transmission of the FSK call information, or if no ACK signal is received by the central office from the integrated CIDCW unit, the central office restores the far-end party""s talking path. The integrated CIDCW unit restores handset (or microphone and speaker) operation upon completion of the reception of the FSK call information.
At any time after a called party having CIDCW service has been alerted to the availability of call information for an incoming call waiting call and while a party is still in the waited state, CIDCW allows the customer to flash the switch hook to retrieve the waited call, and subsequently to go back and forth between the current far-end party and the held party by flashing. CIDCW provides all the capabilities associated with the current CW service, with the additional capability of providing CID data to a customer on waited calls. Therefore, CIDCW is considered an enhancement of the CW service. A telephone line may either have call waiting (CW) or CIDCW service enabled, but not both at the same time.
There is a concern regarding the ability of Type II call related information receiver units (i.e., CIDCW receiver units), whether integrated with or adjunct to the customer premises equipment, to accurately and reliably detect call related information, e.g., alerting CAS tones and subsequent FSK data. This is because the Type II equipment, when in an off-hook condition, may carry a conversation or other information between at least two parties while the alerting CAS tones are received. Thus, it is very possible for voice signals of the conversation to interfere with the call related information, e.g., the alerting CAS tones indicating the availability of call information for an incoming call waiting caller.
FIG. 4 shows the approximate long-term average spectral energy density for continuous speech, indicating that high relative spectral energy is present in near-end speech, which is in the same general range as the alerting CAS tones used to transmit call information such as Caller ID. The presence of speech adds complexity to algorithms employed to detect the alerting CAS tones and, in fact, can cause a false detect (i.e., talkoff) or missed detects (i.e., talkdown) of an alerting CAS tone signal. Thus, conversation can interfere significantly with the reception of call related information at a conventional adjunct CIDCW receiver unit, causing erroneous detection or non-detection of the alerting CAS tones, and erroneous reception or non-reception of call related information such as a telephone number and household name of the incoming call waiting party.
CIDCW data is received when a telephone is off-hook (i.e., in use). To guarantee that the frequency shift keying (FSK) data transmitted after the alerting CAS tones by the central office are not corrupted by conversation, Bellcore recommendation FSD 01-02-1090 suggests muting of the microphone at the customer premises equipment upon detection of the alerting CAS tone sequence, and maintaining the muting until the call information for the call waiting caller is received. Conventional CIDCW customer premises equipment follows the Bellcore recommendation FSD 01-02-1090 (which, in its entirety, is explicitly incorporated herein by reference). For instance, U.S. Pat. No. 5,263,084 and other conventional integrated customer premises equipment systems mute the microphone at the customer premises equipment by switching the microphone out of electrical connection with the customer premises equipment upon detection of the alerting sequence of CAS tones. However, the muting of the alerting CAS tones is not possible in a CIDCW receiver unit because the CIDCW receiver unit does not know, a priori, when the alerting CAS tone will be transmitted. Thus, conventional CIDCW units require the detection of call related information, e.g., at least the alerting CAS tones, in the possible presence of near-end speech.
FIGS. 5 to 7 show a conventional adjunct CIDCW receiver unit 500 in more detail.
In particular, FIG. 5 shows the RJ-11 type connections in a conventional adjunct CIDCW receiver unit 400, both for the customer premises equipment, e.g., a telephone 402, and for the telephone line 404. With these two connections 402, 404, the conventional adjunct CIDCW receiver unit 400 would appear to xe2x80x98interceptxe2x80x99 the signal between the telephone line and, e.g., the telephone. However, this is not the case.
FIG. 6 shows the actual electrical connection of the telephone line between a central office 504, an adjunct CIDCW receiver unit 500, and a telephone 502. The adjunct CIDCW receiver unit 500 is merely xe2x80x98tapped offxe2x80x99 the telephone line at node 506, the two RJ-11 type connectors 402, 404 shown in FIG. 5 being generally for the convenience of the user, to avoid the need for a three-way telephone line tap at node 506. Thus, in conventional adjunct CIDCW receiver units, a direct connection remains between the telephone 502 and the central office 504.
FIG. 7 shows the conventional adjunct CIDCW receiver unit 500 in more detail. In particular, the conventional adjunct CIDCW receiver unit 500 includes a telephone line interface (TLI) 506, and a call related information portion including a codec 524, a digital signal processor (DSP) 520, and a display 544.
The TLI 506 comprises a hybrid or other conventional interface hardware for presenting the proper impedance to the telephone line from the central office 504. The input of the TLI 506 is connected to the telephone line from the central office 504, while the output of the TLI 506 is connected to the codec 524 of the CIDCW receiver unit 500. The codec 524 may be integrated within the DSP 520 or may be separate therefrom.
The DSP 520 is adapted to perform conventional software routines in a CIDCW functional block 540, e.g., FSK demodulation in an FSK demodulator 542a, tone detection in a tone detector 542b, and tone generation in a tone generator 542c. 
The display 544 is adapted to display the pertinent call related information, e.g., the telephone number and/or household name of the calling party.
A keypad (not shown) may be included in the adjunct CIDCW receiver unit 500 to, e.g., allow the user to scroll through a log of previously received call related information on the display 544.
Accordingly, conventional telephone equipment including an integrated CIDCW receiver unit can disconnect or otherwise mute the microphone of a handset or a speakerphone to allow accurate and reliable detection of call related information, e.g., CIDCW FSK data, but only after the initial alerting CAS tones have been detected. Thus, conventional adjunct CIDCW receiver units must analyze the call related information together with possible voice data, reducing the reliability and/or accuracy of the reception of the call related information.
There is thus a need to improve the talkoff (i.e., false detects) and talkdown (i.e., missed detects) performance of adjunct CIDCW receiver units.
In accordance with the principles of the present invention, an adjunct call related information receiver unit comprises a first telephone line interface, and a call related information processor adapted to receive call related information.
A method of receiving call related information in an adjunct call related information receiver is also provided in accordance with the principles of the present invention. The method comprises inserting the adjunct call related information receiver in series between a telephone line from a central office and an associated customer premises equipment. A signal relating to the customer premises equipment is canceled from a signal received from the telephone line, and the call related information is received in a call related information processor.